Branches, Bifurcations and Retroflections over the Tail of the Grand Banks

建议分析现有的数据(水文学、海流计、表层漂浮物、次表层浮游物、高度计和海温观测)，以描述大浅滩尾部的平均和可变(从季节到年际的中尺度)区域环流，最终能够更全面地描述洋流的分支、分叉和反转。在那里，风驱动的主要分支(墨西哥湾流和拉布拉多流)和温盐环流(深西部边界流)相遇，洋流的性质和路径发生了戏剧性的变化。拉布拉多海流和深西部边界海流在浅滩尾部附近部分后向反射，但组合海流损失的输运量和后向反射路径的细节尚不清楚。同样，在大浅滩以南，墨西哥湾流从西向尾部靠近，全深度气流携带着大量的交通工具。在尾部，墨西哥湾流分成四个分支，其中一个关键分支向北穿过尾巴，为大浅滩以东的北大西洋洋流提供水源。将运输准确地划分为不同的分支仍不清楚。深水洋流之间的相互作用似乎受到尾部浅滩地形的强迫和制约，导致温跃层区域性扭曲为尾部a槽上的气旋蜿蜒--在空间和时间上都非常稳定。根据已有的观测结果，我们假设，低谷结构对即将到来的洋流来说是一个瓶颈，限制了横跨尾巴的电流分支的强度。这将是现有数据范围内的定量描述，并可能指向关键的新测量，这些测量将收紧对表征的限制。还将检查高分辨率数值模式的输出，目的是深入了解尾部引起的瓶颈的动力学。

It is proposed to analyze existing data (hydrography, current meter, surface drifter, subsurface float, altimetric and SST observations), to characterize the mean and variable (mesoscale through seasonal to interannual) regional circulation around the Tail of the Grand Banks, ultimately enabling a more complete description of the branches, bifurcations and retroflections of the currents.This is a critical location for the North Atlantic circulation. There, major branches of the wind-driven (Gulf Stream and Labrador Current) and thermohaline circulations (Deep Western Boundary Current) meet, and dramatic changes in the character and pathways of the currents follow. The Labrador Current and Deep Western Boundary Current partially retroflect near the Tail of the Banks, but the amount of transport lost by the combined currents and the details of the retroflection pathway are unknown. Similarly, south of the Grand Banks, the Gulf Stream approaches the Tail from the west with full-depth flow carrying large transport. At the Tail, the Gulf Stream splits into four branches, with a critical branch turning north across the Tail to feed the North Atlantic Current east of the Grand Banks. The exact partitioning of transport into separate branches remains unknown. The interaction between the deep-reaching currents appears forced and constrained by the shoaling topography of the Tail, resulting in a regional distortion of the thermocline into a cyclonic meander over the Tail a trough - remarkably stable in both space and time. Based on existing observations we hypothesize that the trough configuration represents a bottleneck for the approaching currents, limiting the strengths of the current branches crossing the Tail. This will be a quantitative description within the limits of existing data, and may point to critical new measurements that would tighten the constraints on the characterization. The output from high-resolution numerical models will also be examined with the goal of gaining insight into the dynamics of the Tail-induced bottleneck.